Sciencemadness Discussion Board

Is it possible to synthesize phthalic acid [or anhydride] from phthalimide?

SuperOxide - 7-6-2021 at 12:53

I'm well familiar with the synthesis of phthalic anhydride from phthalate based plasticizers, which I have done a few times. And I know that's easily turned into phthalimide using urea or ammonia. However, I was looking to see if there's a known synthesis procedure for going the other direction? I have a decent amount of phthalimide, and there are a few reactions I'd like to try that need phthalic acid/anhydride, and I don't want to have to purchase them or make them again from scratch if I can just use the phthalimide I have on hand that's just been sitting on the shelf collecting dust.

I did look around, and either my Google fu isn't what it use to be, or there isn't too much out there about this.

Thanks.


Oxy - 7-6-2021 at 13:11

Carboxylic acids can be synthesised from amides by hydrolysis in acidic or basic conditions.

basic conditions will produce salt but it's pretty easy to convert it to acid

[Edited on 7-6-2021 by Oxy]

SuperOxide - 7-6-2021 at 14:42

Quote: Originally posted by Oxy  
Carboxylic acids can be synthesised from amides by hydrolysis in acidic or basic conditions.

basic conditions will produce salt but it's pretty easy to convert it to acid


Thanks, Oxy. This looks right: http://www.chem.ucalgary.ca/courses/350/Carey5th/Ch22/ch22-2... - I'll give that as hot.

[Edited on 7-6-2021 by SuperOxide]

zed - 8-6-2021 at 01:06

Hydrolysis of Phthalimide might not be really easy.

I'd look for a published procedure.

Triflic Acid - 8-6-2021 at 05:33

Amide hydrolysis is generally a pain. Might be worth trying http://www.sciencemadness.org/talk/viewthread.php?tid=79854

SuperOxide - 8-6-2021 at 06:34

Yeahhh, I did a little more research, it looks like it would be better to just re-make the phthalates, or buy some.

As always, thanks for the input.

clearly_not_atara - 8-6-2021 at 09:05

If you have hydrazine handy, phthalimide rapidly converts to the cyclic hydrazide. Then oxidizing this gives a 2,3-diazanaphthoquinone that should easily undergo acidic hydrolysis. Nothing is easier than buying more, of course.

SuperOxide - 8-6-2021 at 10:56

Quote: Originally posted by clearly_not_atara  
If you have hydrazine handy, phthalimide rapidly converts to the cyclic hydrazide. Then oxidizing this gives a 2,3-diazanaphthoquinone that should easily undergo acidic hydrolysis. Nothing is easier than buying more, of course.


Yeah, I saw this when I was researching the reaction. I don't have any hydrazine handy at the moment, though that's on my to-do list (maybe this weekend).

I may do it anyways (on a smaller scale) just as an experiment to learn about the reaction a bit.

[Edited on 8-6-2021 by SuperOxide]